Rheostat



Jan. 5, 1937. D. F. HASTINGS RHEOSTAT v Filed Aug. 21, 1936 INVENTOR Jorgafif'fpslfgi 2a. mfw ATTORNEY mama Jan. 5, 1931 PATENT: oFFicE RHEOSTA'I Donaldl Hastings, Radburn, Fair lawn, N. 1., aslignor to Hardwick, Kindle, Ina, Newark,

Applioatien august 21, 1938, SerialNo. cuss 9 Claims. (01. 20l56) This invention relates to a rheostat of the variable type.

It is one of the objects of my invention to provide a variable power rheostatin which all the parts carrying current, usually referred to as "live parts, are, with the possible exception of the terminals, completely enclosed, thereby preventing interference with the rotating brush adjustment, and short-circuiting ofany of the interior current-conducting parts, at tlm same time protecting the brush track surface and the winding from dirt and mechanical injury.

Another object of my invention is to provide a' rheostat which is compact in design and in which the exposed surface or face away from the mounting panel has no projecting parts, thereby presenting a smooth or flush surface, which reduces the chances for damage to the rheostat, as well as presenting a better appearing instrument.

Another object of my invention is to provide a rheostat in which the winding terminal connections are positively positioned so that they can-'- not be shifted into engagement with one another.

Another object of my invention is to provide a good, continuous and permanent electrical circuit between the outside terminal post and the brush.

These and other objects will be clear to one familiar with the rheostat art, from a reading of the attached specification, taken in connection with the annexed drawing, wherein? Figure 1 is aview of the face side of the rheostat, a part of the front cover plate being broken away to show some of the interior parts.

Figure 2 is a vertical, sectional view on the line- 2--2 of Figure 1.

Flgure3 is a perspective, fragmentary view of the recessed portion of that part of the winding core which carries the terminal clips.

Figure 4 is a face view of the left-hand side of the insulator carrying the moving brush, looking at Figure 2.

Figure 5 is a view of the closure disc used for sealing the face of the insulator carrying the Figure 6 is a plan view of the spring member shown in Figure 2, for laterally positioning the operating shaft.

In the various views, wherein like numbers refer to corresponding parts, I is a mounting plate, preferably of metal and having a flange 2 adapted to engage a mounting member 3. A core 5, preferably of ceramic material of high heat-. resisting qualities, is fastened to the mounting plate I by means of two screws 5 at the terminal side of the rheostat. The screws 5 pass through holes 5 in bosses I which project into engagement with the plate I. At'what might be considered the top of the rheostat, a bushing 8 of ceramic material is fastened to the mounting plate i as by means of a rivet or eyelet 9. The bushing 8 is cemented to the vitreous enamel which is appliedto the resistance winding i0 after this has been wound on the core 4.

The bottom or terminal part of the core has a recessed portion adjacent the bosses This recessed portion is divided into what maybe termed three compartments il, i2, and I3, which are separated by ledges l4 preferably moulded integral with the core. A brush clip l5, having an inwardly bent portion i5, is seated in the compartment l2 and fastened therein by a brushmember 20 to be later described. The .end I! a of the clip 15 projects into an annular recess 21 in an insulator 22, preferably of ceramic or other high heat-resisting insulating material. Positioned in the annular recess 2|, is a flexible conductor 22 of any suitable material such as springtempered, phosphor bronze, one end of which is securely fastened at 24 to the end ll of the clip' l5. The other end of the spirally wound conductor 22 is fastened to a brush or shoe 25 in any satisfactory manner as by moulding the same therein.

The brush 25 is seated in apocket 25 moulded in the insulator 22. The pocket 25 has an open ing through which the brush 25 projects into contact with the track 21 formed on the core member 4 when the vitreous enamel is applied to the winding; that is to say, the vitreous enamel is removed from the inner peripheral surface of the winding II to leave the inner turns of thewinding bare to provide the track 21 for the brush 25. Another opening out of the pocket 25 allows a reduced end 2| of the brush 25 to project resisting material, such as mica, is fastened to the inner side of the insulator 22 in any satisfactory manner as by rivets or eyelets 32, thereby sealing up the annular recess 2| and also covering the brush pocket 26. Thus, if the spiral conductor 23 should become overheated and sag or burn out, or become broken, or the spring 3' become damaged in any way, the pieces are held in the annular recess and cannot get out into the rheostat and do damage. These parts being so positioned and protected as described, they cannot be readily tampered with.

The insulator 22 has a hub 33 which projects toward and in close proximity to the mounting plate I. Passing through the hub 33 is an operating shaft 34 carried by a bushing 35 fastened to the mounting plate I in any satisfactory manner, two nuts 36 being indicated for this purpose. A nut 53 is used for mounting the rheostat on the panel 3. The end of the shaft 34 has a metal upset thereon or a pin 39 adapted to be positioned in notches 40 in the outer face of the member 22, thereby completing the driving connection between the member 22 and the shaft 34 which is held in position on the bushing by means of a lock ring in the groove 4| cut in the shaft. A spring tension member 42 is preferably used to hold the shaft in its lateral operative position.

Closing the three holes 43 which receive the rivets or eyelets 32, as well as the recess for the end of the shaft 34, is a plate 44 of heat-resisting material and preferably of metal, which also acts as a name plate for the rheostat. The plate 44 is fastened to the member 22 by a pair of eyelets passing through the holes 45 into the member 22.

Positioned in the compartments II and ii, are terminal clips 46 shown in dotted linm in Figure 1, they being held in their respective compartments by terminal screws 41 and 43. It will be noted from Figure 3, that there is a flange 49 along one edge of the core.which, together with the ledges l4, position the terminal clips 40. At the base of the'fiange 49, in both of the compartments l I and I3, there is a slot 5| passing all the way through the flange. The slots 50 are provided to receive the ends of the winding M which are passed therethrough and then fastened to the clips 46 as by soldering, or the end of the winding may pass under the clips and be clamped in position by the terminal screws 41 and 48.

Each of the clips 46 has a projecting portion II which, in the assembly operation, is bent so as to lie in the arcuateplane ofthetrack2lsothat, when the brush 25 reaches the end of its travel in either direction of rotation, it will have one of the fiat surfaces 5| of the terminal clips 46 to travel on. The hub 33 of the insulator 22 has a rib I2 which is adapted to engage the central clip I! which acts as a stop, the rib 52 hitting the member I! when the brush 25 passes into engagement with the parts 5i as just described.

From what has been said, and referring particularly to Figure 2, it will be seen that a smooth or fiat surface is obtained on what may be considered theface of the rheostat, so that there are no projecting parts on the face to be accidentally hit and broken. Also, it will be noted that all the movable parts of the rheostat are housed in such a manner that they are fully protected, and at the same time the core and its winding are arranged so as toprovide good ventilation, whereby the heat may be conducted rapidly away from the rheostat.

- terminal screws ,41, 48, and I1.

aoeaasa With such a construction, the separate housing formerly used on many types of rheostats is not required, and if desired, a removable cover held by the screws 5 may be applied over the three It may also be noted that the mounting plate I is provided with a pair of bosses having tapped holes therein for fastening the rheostat to the mounting 3, but in the views taken, these bosses are not shown.

What I claim is:

1. In a rheostat, a mounting plate, an annular core of ceramic material fastened to said plate, said core having a recessed portion with terminal studs positioned in the wall of the core and connected to contact clips located within the recess, a winding on the core terminating at the opposite ends of the recess and connected to contact clips at these'ends, said winding being covered with a coating of vitreous enamel except for its inner peripheral surface which is bared to provide a brush track, a shaft rotatably carried by said mounting plate, a circular insulator preferably of ceramic material carried by said shaft for rotation therewith, said insulator having a centrally located annular recess and a pocket adjacent said recess, said pocket opening on one side into the recess and opening on the opposite side toward said winding track, a brush located in said pocket and having parts projecting through both of said openings, one projecting part contacting with said winding track, a spring in the pocket for urging said brush radially into contact with the winding track, a conductor spirally arranged in said annular recess and having one end connected to said brush, a centrally located brush terminal in said recessed portion of said core and having a projecting part extending into said annular recess and connected to the said spirally arranged conductor, a disc-shaped insulator fastened to the first mentioned insulator and covering said annular recess and pocket.

2 A rheostat as defined in claim 1 further characterized in that said first mentioned insulator has a hub extending toward and closely to the mounting plate, said hub having a stop rib thereon adapted to engage said centrally located brush terminal to limit the movement of rotation of said shaft and brush.

3. A rheostat as defined in claim 1 further characterized in that said first mentioned insulator has a hub extending toward and closely to the mounting plate, said hub having a stop rib thereon adapted to engage said centrally located brush terminal to limit the movement of rotation of said shaft and brush and still further characterized in that said first mentioned insulator has its outer face covered by a circular name plate preferably of metal which is positioned substantially flush with the side of said wound core."

4. In a rheostat, a mounting plate, an annular core of ceramic material fastened to said plate, said core having a recessed portion with terminal studs positioned in the wall of the core and connected to contact clips located within the recess, a winding on the core terminating at the opposite ends of the recess and connected to contact clips at these ends, said winding being covered with a coating of vitreous enamel except for its inner peripheral surface which is hated to provide a brush track, a substantially sealed rotatable unit carried by the mounting plate, said unit including an insulator preferably of ceramic material having a hub drivingiy carried on a shaft supported in a bushing in'said plate, the said insulator having an annular recess-around the 1 tending into said annular recess and connected to said spirally arranged conductor, a flre proof insulator closing the annular recess and a fire proof disc positioned over the outer face of the brush carrying insulator.

5. In a rheostat, a flanged metal mounting plate having a centrally located bearing bushing, an annular core of ceramic material carrying a winding covered with vitreous material except for an interior track surface on the winding, said core being-fastened to said plate and carrying contact clips for the ends of the winding and a brush contact clip, a sealed rotatable unit positioned within the confines of said core, said unit including a circular fire proof insulator having a ribbed hub projecting toward the mounting plate and a shaft passing through the hub and said plate bushing, and being drivingly fastened to said insulator, a brush mounted in the insulator and a spring pushing the brush radially into contact with the winding track, a conductor attached at one end to the brush and spirally arranged in a recess around said hub and connected to said brush clip which also acts as a stop to be engaged by said hub'rib, a fire proof disc fastened to the inner faceof said insulator and sealing the side of the insulator and a fire proof disc acting also as a name plate fastened to the outer side of the insulator and closing oil all openings in this side of the insulator.

6. A rheostat as set forth in claim 6 further 40 characterized in that the said core has a recessed in either direction of rotation.

7. A rheostat as set forth in claim 5 further characterized in that the said core has a recessed portion with a flange along one edge and provided with transverse ledges separating the recessed portion into compartments for positioning said contact clips, the flange at the end compartment having slots therein for bringing the ends of the winding into their respective compartments for attachment to the clip and terminal therein.

8. In a rheostat, a mounting plate, a core having a winding fastened to but spaced from said plate, a shaft carried by said plate, a circular insulator fastened to the shaft within the confines of the core, said insulator being of a thickness substantially the same as that of the core and having a hub for the shaft with an annular recess around the hub and also a pocket near the edge of the insulator, aspring and brush mounted in said pocket, the brush extending through an opening in the pocket into contact with the track' surface provided on the winding,

, a conductor spirally arranged in said recess and having one end connected to the brush, said core having a recessed portion divided into three compartments, a brush terminal clip mounted in the central compartment and having one end fastened to said conductor, terminal clips located in the other of said compartments, one on each side of the central compartment and means for connecting said last mentioned clips to ,the ends of the winding and covering discs for both sides of said insulator, the outer disc coming substantially flush with the plane of the face of the wound core.

9. In a rheostat, a mounting plate, a core having a winding fastened to but spaced from said plate, a shaft carried by said plate, a circular insulator fastened to the shaft within the confines of the core, said insulator being of a thickness substantially the same as that of the core and having a hub for the shaft with an annular recess around the hub and also a pocket near the edge of the insulator, a spring and brush mounted in said Docket. the brush extending through an opening in the pocket into contact with the track surface provided on the winding,

nonam 1'. names. 

